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Sex differences in infant body composition emerge in the first 5 months of life

Shanlee M Davis1,2, Jill L Kaar3, Brandy M Ringham4

  • 1University of Colorado, Department of Pediatrics, Denver, USA.

Journal of Pediatric Endocrinology & Metabolism : JPEM
|September 5, 2019
PubMed

Insights

Male infants accumulate less body fat than females within the first five months of life. This sex difference in body composition may be influenced by early testosterone production in males.

Area of Science:

  • Human physiology
  • Pediatric endocrinology
  • Body composition analysis

Background:

  • Sex differences in body composition are influenced by sex steroids like testosterone and estrogen.
  • These differences are observed throughout the lifespan.
  • Early life hormonal influences on body composition are not fully understood.

Purpose of the Study:

  • To investigate the emergence of sex differences in body composition during the first months of life in healthy infants.
  • To correlate these differences with the onset of endogenous testosterone production in males.

Main Methods:

  • Longitudinal observational study of 602 healthy infants.
  • Measurement of linear growth and body composition using air displacement plethysmography at birth and 5 months.
  • Comparison of the rate of change in body composition parameters between sexes.

Main Results:

  • Significant sex differences in length, total mass, fat-free mass (FFM), and percent fat mass (%FM) were observed at birth and 5 months (p < 0.001).
  • Males exhibited greater total mass and FFM but lower %FM compared to females.
  • Males had a significantly lower gain in %FM over the first 5 months (p = 0.0004), attributed to higher FFM gain.

Conclusions:

  • Sex differences in infant body composition are evident within the first months of life.
  • Males show reduced adiposity accumulation compared to females.
  • Early endogenous testosterone production in males may drive these observed body composition differences, potentially impacting lifelong development.

Keywords:
PEA PODadipose tissuebody compositionbody fat percentagecritical windowmini-puberty

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